10. spindle assembly checkpoint

Question 1

2 factors necessary to establish bi-orientation of the sister chromatids

Answer 1

Attachment of microtubules to the kinetochore

Tension applied across the sister chromatids

Question 2

How are the sister chromatids separated when all are bi-orientated

Answer 2

Scc1 of the cohesion complex is cleaved by Seperase

Question 3

What usually keeps Seperase inactive and what stops this inactivation?

Answer 3

Securin inhibitor protein
When all sister chromatids are bioriented on the mitotic spindle the APC/C (a E3 ubiquitin ligase ) is activated in conjugation with Cdc20 . Ubiquitinates securin

Question 4

As well as securin degradation what does the APC/C degrade?

Answer 4

Cyclin B

Question 5

What associates to Cdc20 when microtubules are not fully attached to kinetochores or sister chromatid pairs are not under tension?

Answer 5

Mad1, Mad 2, BubR1, Bub3.